Physiological effects of consumption of resistant starch

Resistant starch (RS) is defined as the sum of starch and products of starch degradation not absorbed in the small intestine of healthy individuals. Thus, RS enters the colon where it may be fermented. In this respect, RS resembles some types of dietary fibre. Three types of RS are being discerned: RS ₁ , physically entrapped starch; RS ₂ , uncooked starch granules; RS ₃ , retrograded starch. The estimated current mean per capita RS intake in the Netherlands is 5 g/d. The amount of RS in foods can be manipulated by the choice of raw products and food processing techniques. This is of potential interest if an increased RS consumption would be beneficial for human health. In this thesis several of the hypotheses concerning putative positive effects of RS consumption on human physiology are studied. Daily consumption of up to 32 g RS ₂ or RS ₃ was tolerated well by healthy individuals and increased colonic fermentative activity and stool weight. Replacement of 27 g digestible starch by RS ₂ reduced diet-induced thermogenesis and postprandial glucose and insulin responses proportionally to the amount of indigestible carbohydrate consumed. When compared with an equivalent amount of glucose, daily supplementation of 30 g RS ₂ or RS ₃ for 3 wk did not affect serum lipid concentrations in healthy subjects, and daily supplementation with 32 g RS ₂ or RS ₃ for 1 wk did not affect putative risk factors for colon cancer, subjective feelings of hunger, faecal ammonia excretion and apparent absorption of magnesium, calcium and phosphorus in healthy individuals. No differences were observed between RS ₂ and RS ₃ , in the parameters studied. In piglets, dietary RS ₃ , but not RS ₂ , shifted nitrogen excretion from urine to faeces, and RS ₂ reduced apparent magnesium and calcium absorption. In rats, dietary RS ₂ , but not RS ₃ , increased apparent, but not true magnesium absorption. It was concluded that daily consumption of up to 32 g RS ₂ or RS ₃ , is not unfavourable for healthy individuals, but it also does not have great beneficial effects on human physiology, at least for the parameters and time span studied in this thesis. Especially the significance for human health of increased activity and site of fermentation in the colon, and the possible role of the various types of RS in the prevention of colon cancer should be studied further.